Chilled ammonia based CO2 capture system with water wash system

ABSTRACT

A method and system for reducing an amount of ammonia in a flue gas stream. The system  100  includes: a wash vessel  180  for receiving an ammonia-containing flue gas stream  170 , the wash vessel  180  including a first absorption stage  181   a  and a second absorption stage  181   b , each of the first absorption stage  181   a  and the second absorption stage  181   b  having a mass transfer device  184 ; and a liquid  187  introduced to the wash vessel  180 , the liquid  187  for absorbing ammonia from the ammonia-containing flue gas stream  170  thereby forming an ammonia-rich liquid  192  and a reduced ammonia containing flue gas stream  190  exiting the wash vessel  180.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No.61/102,137 filed on Oct. 2, 2008 and U.S. provisional application No.61/102,217 filed on Oct. 2, 2008, the contents of which are incorporatedherein by reference in their entireties.

FIELD

The disclosed subject matter relates to a system and method for removingcarbon dioxide (CO₂) and ammonia (NH₃) from a flue gas stream. Morespecifically, the disclosed subject matter relates to a system andmethod employing a multi-stage wash vessel for removing ammonia from aflue gas stream that has been subjected to a CO₂ removal system andprocess.

BACKGROUND

Most of the energy used in the world is derived from the combustion ofcarbon and hydrogen-containing fuels such as coal, oil and natural gas.In addition to carbon and hydrogen, these fuels contain oxygen, moistureand contaminants such as ash, sulfur (often in the form of sulfuroxides, referred to as “SOx”), nitrogen compounds (often in the form ofnitrogen oxides, referred to as “NOx”), chlorine, mercury, and othertrace elements. Awareness regarding the damaging effects of thecontaminants released during combustion triggers the enforcement of evermore stringent limits on emissions from power plants, refineries andother industrial processes. There is an increased pressure on operatorsof such plants to achieve near zero emission of contaminants.

Numerous processes and systems have been developed in response to thedesire to achieve near zero emission of contaminants. Systems andprocesses include, but are not limited to desulfurization systems (knownas wet flue gas desulfurization “WFGD” and dry flue gas desulfurization“DFGD”), particulate filters (including, for example, bag houses,particulate collectors, and the like), as well as the use of one or moresorbents that absorb contaminants from the flue gas. Examples ofsorbents include, but are not limited to, activated carbon, ammonia,limestone, and the like.

It has been shown that ammonia efficiently removes CO₂, as well as othercontaminants, such as sulfur dioxide (SO₂) and hydrogen chloride (HCl),from a flue gas stream. In one particular application, absorption andremoval of CO₂ from a flue gas stream with ammonia is conducted at a lowtemperature, for example, between 0 and 20 degrees Celsius (0°-20° C.).To safeguard the efficiency of the system, and to comply with emissionstandards, maintenance of the ammonia within the flue gas streamtreatment system is desired.

SUMMARY

According to aspects illustrated herein, there is provided a system forreducing an amount of ammonia in a flue gas stream, the systemcomprising: a wash vessel for receiving an ammonia-containing flue gasstream, the wash vessel including a first absorption stage and a secondabsorption stage, each of the first absorption stage and the secondabsorption stage having a mass transfer device; and a liquid introducedto the wash vessel, the liquid for absorbing ammonia from theammonia-containing flue gas stream thereby forming an ammonia-richliquid and a reduced ammonia containing flue gas stream exiting the washvessel.

According to other aspects illustrated herein, there is provided asystem for reducing an amount of ammonia in a flue gas stream, thesystem comprising: an absorbing system having one or more absorbers toabsorb carbon dioxide (CO₂) from a cooled flue gas stream having atemperature below ambient temperature, the absorbing system operates ata temperature between 0° and 20° Celsius, wherein at least a portion ofthe CO₂ is absorbed by an ammoniated solution or slurry therebyproducing an ammonia-containing flue gas stream; and a wash vesselconfigured to receive at least a portion of the ammonia-containing fluegas stream, the wash vessel includes one or more absorption stages, eachof the one or more absorption stages having a spray head system and amass transfer device selected from random packing material, hydrophilicpacking material, and structural packing, wherein the spray head systemdirects a liquid in a direction countercurrent to a direction of theammonia-containing flue gas stream, the liquid absorbing ammonia fromthe ammonia-containing flue gas stream and thereby forming anammonia-rich liquid and a reduced-ammonia flue gas stream, whereby atleast a portion of ammonia present in the ammonia-containing flue gasstream is removed from the ammonia-containing flue gas stream in the oneor more absorption stages of the wash vessel.

According to other aspects illustrated herein, there is provided amethod of reducing an amount of ammonia from a flue gas stream, themethod comprising: introducing a cooled flue gas stream having atemperature below ambient temperature to an absorbing system, whereinthe absorbing system operates at a temperature between 0° and 20°Celsius; contacting the cooled flue gas stream in the absorbing systemwith an ammoniated slurry or solution, wherein the ammoniated slurry orsolution removes carbon dioxide (CO₂) from the cooled flue gas streamthereby forming an ammonia-containing flue gas stream; and introducingat least a portion of the ammonia-containing flue gas stream to a washvessel, the wash vessel having one or more absorption stages to absorbammonia from the ammonia-containing flue gas stream thereby reducing anamount of ammonia in a flue gas stream exiting the wash vessel.

The above described and other features are exemplified by the followingfigures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, which are exemplary embodiments, andwherein the like elements are numbered alike:

FIG. 1 is a schematic representation of a system used to reduce anamount of CO₂ and ammonia present in a flue gas stream.

FIG. 2 is an illustration of one embodiment of an absorbing systemutilized in the system depicted in FIG. 1.

FIG. 3 is an illustration of one embodiment of a wash vessel utilized inthe system depicted in FIG. 1.

DETAILED DESCRIPTION

In one embodiment, as shown in FIG. 1, a system 100 for reducing anamount of ammonia (NH₃) and carbon dioxide (CO₂) present in a flue gasstream includes several devices and processes for removing a variety ofcontaminants from a flue gas stream 120 generated by combustion of afuel in a furnace 122. As shown in FIG. 1, system 100 includes anabsorbing system 130 to absorb carbon dioxide (CO₂) from the flue gasstream 120 and, in one embodiment, a cooled flue gas stream 140.

Cooled flue gas stream 140 is generated by passing the flue gas stream120 generated by the combustion of a fuel in a furnace 122 to a coolingsystem 142. Before introduction to the cooling system 142, flue gasstream 120 may undergo treatment to remove contaminants therefrom, suchas, for example, a flue gas desulfurization process and particulatecollector, (not shown).

Cooling system 142 may be any system that can produce cooled flue gasstream 140, and may include, as shown in FIG. 1, a direct contact cooler144, one or more cooling towers 146 and one or more chillers 148, thatwash and/or scrub the flue gas stream 120, capture contaminants, and/orlower the moisture content of the flue gas stream. However, it iscontemplated that cooling system 142 may include less or more devicesthan are shown in FIG. 1.

In one embodiment, the cooled flue gas stream 140 has a temperature thatis lower than the ambient temperature. In one example, cooled flue gasstream 140 may have a temperature between about zero degrees Celsius andabout twenty degrees Celsius (0° C.-20° C.). In another embodiment, thecooled flue gas stream 140 may have a temperature between about zerodegrees Celsius and about ten degrees Celsius (0° C.-10° C.).

As shown in FIG. 1, cooling system 142 is in communication with theabsorbing system 130. It is contemplated that the cooling system 142 maybe in direct communication with the absorbing system 130, i.e., thereare no additional processes or devices between the cooling system andthe absorbing system. Alternatively, the cooling system 142 may be inindirect communication with the absorbing system 130, i.e., there may beadditional processes or devices between the cooling system and theabsorbing system, such as, but not limited to, particulate collectors,mist eliminators, and the like.

Absorbing system 130 facilitates the absorption of CO₂ from the cooledflue gas stream 140 by contacting the cooled flue gas stream with anammoniated solution or slurry 150. Ammoniated solution or slurry 150 mayinclude dissolved ammonia and CO₂ species in a water solution and mayalso include precipitated solids of ammonium bicarbonate.

In one embodiment, absorbing system 130 includes a first absorber 132and a second absorber 134. However, it is contemplated that absorbingsystem 130 may include more or less absorbers as illustrated in FIG. 1.Additionally, it is contemplated that first absorber 132 and/or secondabsorber 134 may have one or more stages therein for absorbing CO₂ fromthe cooled flue gas stream 140.

The ammoniated solution or slurry 150 introduced to the absorbing system130 may be recycled and/or provided by a regeneration tower 160. Asshown in FIG. 1, ammoniated solution or slurry 150 may be introduced tothe absorbing system 130 at a location within the first absorber 132,however it is contemplated that the ammoniated solution or slurry mayalso be introduced at a location within the second absorber 134 or anyof the absorbers present in the absorbing system 130. Regeneration tower160 is in direct or indirect communication with absorbing system 130.

As shown in more detail in FIG. 2, ammoniated slurry or solution 150 isintroduced to absorbing system 130, e.g., in first absorber 132 orsecond absorber 134, in a direction A that is countercurrent to a flow Bof cooled flue gas stream 140. As the ammoniated slurry or solution 150contacts cooled flue gas stream 140, CO₂ present in the cooled flue gasstream is absorbed and removed therefrom, thereby forming a CO₂-richstream 152. At least a portion of the resulting CO₂-rich stream 152 istransported from the absorbing system 130 to regeneration tower 160.

It is contemplated that either a portion or all of CO₂ rich stream 152may be transferred to regeneration tower 160. As shown in FIG. 1, atleast a portion of CO₂-rich stream 152 may pass through a buffer tank162, a high pressure pump 164 and a heat exchanger 166 prior to beingintroduced to regeneration tower 160. In one embodiment, a separateportion of the CO₂-rich stream 152 may be passed from absorbing system130 through a heat exchanger 168 where it is cooled prior to beingreturned to the absorbing system. Heat exchanger 168 is in communicationwith a cooling system 169. As shown in FIG. 1, the cooling system 169may have a direct contact chiller 169 a as well as a cooling tower 169b; however, it is recognized the cooling system 169 may have more orless devices than what is illustrated herein. The CO₂-rich stream 152 iscooled prior to it being introduced into the absorbing system 130 withthe ammoniated solution or slurry 150.

Additionally, while not shown in FIG. 1 or 2, it is also contemplatedthat the portion of the CO₂-rich stream 152 may be transferred directlyto the regeneration tower 160 without passing through the buffer tank162, the high pressure pump 164 and the heat exchanger 166.

Regeneration tower 160 regenerates the CO₂-rich stream 152 to form theammoniated slurry or solution 150 that is introduced to the absorbingsystem 130. Regeneration tower 160 facilitates the regeneration of usedammoniated solution or slurry, i.e., the CO₂-rich stream 152, which hasbeen through the absorbing system 130 and removed CO₂. Regeneration isperformed by providing heat at the bottom of the regeneration tower 160.Regeneration of the CO₂-rich stream 152 is also performed at highpressure.

The capacity of the ammoniated solution or slurry 150 to absorb CO₂ fromthe cooled flue gas stream 140 depends on, e.g., the ammoniaconcentration in the ammoniated solution or slurry, the NH3/CO₂ moleratio, and the temperature and pressure of the absorbing system 130. Inone embodiment, the NH3/CO₂ mole ratio for absorption of CO₂ is betweenabout 1.0 and about 4.0. In another embodiment, the NH3/CO₂ mole ratiofor absorption of CO₂ is between about 1.0 and about 3.0. Additionally,in one embodiment, the absorbing system 130 operates at a lowtemperature, particularly at a temperature less than about twentydegrees Celsius (20° C.). In one embodiment, the absorbing system 130operates at a temperature between about zero degrees Celsius and abouttwenty degrees Celsius (0° and 20° C.). In another embodiment, theabsorbing system 130 operates at a temperature between about zerodegrees Celsius and about ten degrees Celsius (0° and 10° C.).

As shown in FIGS. 1 and 2, and discussed above, after cooled flue gasstream 140 contacts ammoniated solution or slurry 150, CO₂-rich stream152 is formed, as well as an ammonia-containing flue gas stream 170.Typically, the concentration of ammonia in the ammonia-containing fluegas stream 170 will vary depending on the system, the amount ofammoniated solution or slurry 150 introduced to the absorbing system130, and the amount of the CO₂ present in the cooled flue gas stream140, and therefore, the ammonia-containing flue gas stream may containany concentration of ammonia. In one embodiment, the concentration ofammonia in the ammonia-containing flue gas stream 170 may be betweenabout five hundred parts per million (500 ppm) and about thirty thousandparts per million (30,000 ppm).

It is contemplated that the concentration of ammonia present in theammonia-containing flue gas stream 170 may be measured. For example, theammonia concentration in the ammonia-containing flue gas stream 170 maybe measured by, for example, a dragger tube or Fourier transforminfrared spectroscopy (FTIR). While not shown, the amount orconcentration of ammonia in the ammonia-containing flue gas stream 170may be measured at any point prior to its introduction to a wash vessel180. Measurement of the amount or concentration of the ammonia in theammonia-containing flue gas stream 170 may assist the operator of system100 in removing or reducing the amount of ammonia in theammonia-containing flue gas stream.

As shown in FIG. 1, ammonia-containing flue gas stream 170 is introducedto the wash vessel 180. In one embodiment, wash vessel 180 reduces anamount of ammonia present in the ammonia-containing flue gas stream 170and forms a reduced ammonia-containing flue gas stream 190. However, itis contemplated that wash vessel 180 may be used in conjunction withother systems and methods that generate a flue gas stream containingammonia, i.e., the wash vessel may be used in a system that does notcontain absorbing system 130 and/or cooling system 142.

The reduced ammonia-containing flue gas stream 190 may be released tothe environment. The reduced ammonia-containing flue gas stream 190 maybe directly released to the environment from wash vessel 180. However,it is contemplated that the reduced ammonia-containing flue gas streammay be further processed prior to being emitted to the environment, forexample, it may be washed in an acidic solution to further reducecontaminant content. Additionally, and while not shown in FIG. 1, it iscontemplated that the amount of ammonia present in the reducedammonia-containing flue gas stream 190 may be measured after the reducedammonia-containing flue gas stream exits the wash vessel 180.

In one embodiment, wash vessel 180 is configured to acceptammonia-containing flue gas stream 170. As shown in FIG. 3, wash vessel180 may have an opening 182 at a bottom of the wash vessel that allowsthe ammonia-containing flue gas stream 170 to flow into the wash vessel.While the opening 182 is shown at the bottom of the wash vessel 180, itis contemplated that the opening may be at any point in the wash vesseland may vary from system to system depending on the application.

Wash vessel 180 may have one or more absorption stages, shown generallyat 181, to absorb ammonia from the ammonia-containing flue gas stream170. In one embodiment, as shown in FIG. 3, wash vessel 180 includes twoabsorption stages, a first absorption stage 181 a and a secondabsorption stage 181 b. The wash vessel 180 is not limited in thisregard as it is contemplated that the wash vessel may have more or lessabsorption stages. Each of the absorption stages 181, e.g., first andsecond absorption stages 181 a and 181 b, may include a mass transferdevice 184, a spray head system 186 and a liquid delivery path 188.

The mass transfer device 184 may include packing, such as, for example,random packing, hydrophilic packing, and/or structural packing. Randompacking is generally known in the art and refers to packing materialintroduced to the absorption stage in an un-organized fashion. Examplesof random packing include, but are not limited to plastic, metal and/orceramic packing material offered in different sizes, e.g., materialhaving varying diameters, for example, diameters ranging between about2.5 centimeters (2.5 cm) to about 7.6 centimeters (7.6 cm) (about 1 inchto about 3 inches). Random packing material is available from manysuppliers, including, but not limited to Jaeger Products Inc. (Houston,Tex., United States). Random packing material may also include wood.Hydrophilic packing includes, but is not limited to polypropylene bags.

Structural packing is generally known in the art and refers to packingmaterial that is arranged or organized in a specific fashion. Typically,structural packing is arranged in a manner to force fluids to take acomplicated path, thereby creating a large surface area for contactbetween the liquid and gas. Structural packing includes, but is notlimited to structures made of metal, plastic, wood, and the like. It iscontemplated that different packing materials facilitate ammonia removalor reduction at different flow rates of a liquid into the wash vessel180. Additionally, it is contemplated that the different packingmaterials may provide more suitable pressure drops.

In one embodiment, one of the absorption stages 181 of the wash vessel180 includes random packing material as the mass transfer device 184 andanother of the absorption stages 181 of the wash vessel 180 includesstructural packing as the mass transfer device. For example, firstabsorption stage 181 a may include random packing material as the masstransfer device 184 and second absorption stage 181 b may includestructural packing as the mass transfer device. It is contemplated thatthe ammonia-containing flue gas stream 170 enters the wash vessel 180and passes through the second absorption stage 181 b prior to passingthrough the first absorption stage 181 a.

As shown in FIG. 3, in each of the absorption stages 181, the masstransfer device 184 is located beneath the spray head system 186. Eachof the spray head system 186 in wash vessel 180 sprays a liquid 187 intothe absorption stages 181. The liquid 187 is transported to the sprayhead system 186 via the liquid delivery path 188. The liquid deliverypath 188 is a conduit that transports the liquid 187 to the spray headsystem 186. The liquid 187 may be any liquid suitable to facilitate theremoval of ammonia from the ammonia-containing flue gas stream 170. Anexample of liquid 187 is water, which is known to absorb, i.e.,dissolve, ammonia through interactions between the ammonia and thewater.

In one particular embodiment, liquid 187 introduced to the firstabsorption stage 181 a is liquid 187 a, e.g., water provided by astripping column 194. The liquid 187 provided to the second absorptionstage 181 b is liquid 187 b, which is water-containing low concentrationammonia and CO₂ recycled from the bottom of the wash vessel 180 andpassed through a heat exchanger 189.

The liquid 187 is introduced at the top of each absorption stage 181,e.g., liquid 181 a is provided to the top of first absorption stage 181a and liquid 187 b is provided to the top of second absorption stage 181b, of the wash vessel 180. The liquid 187 travels in a direction C downa length L of the wash vessel 180, which is countercurrent to adirection D that the ammonia-containing flue gas stream 170 travels upthe length L of the wash vessel 180. As will be appreciated, the liquid187 travels in direction C by virtue of gravity, while theammonia-containing flue gas stream 170 travels in direction D by virtueof several factors, including pressure drops within the wash vessel 180.

As the liquid 187 travels in the direction C, it passes through the masstransfer devices 184 in each of the absorption stages 181. Likewise, asthe ammonia-containing flue gas stream 170 travels in direction D, itpasses through the mass transfer devices 184 in each of the absorptionstages 181.

As the liquid 187 travels in direction C down the length L of the washvessel 180, the ammonia concentration in the liquid increases, therebyforming an ammonia-rich liquid 192. Conversely, as theammonia-containing flue gas stream 170 travels in a direction D up alength, e.g., the length L, of the wash vessel 180, the ammoniaconcentration in the ammonia-containing flue gas stream decreasesthereby forming the reduced ammonia-containing flue gas stream 190.

For example, liquid 187 a is introduced at the top of wash vessel 180through a spray head system 186 over the first absorption stage 181 aand travels in a direction C down the length L of the wash vessel. Theconcentration of ammonia present in the liquid 187 a exiting the firstabsorption stage 181 a is higher than the ammonia concentration of theliquid 187 a entering the first absorption stage 181 a since the liquidhas contacted the ammonia-containing flue gas stream 170 that travels indirection D up the length L of the wash vessel and absorbed ammoniatherefrom. In this embodiment, a greater percentage of ammonia in theammonia-containing flue gas stream 170 is absorbed by the liquid 187 athat flows from the first absorption stage 181 a to the secondabsorption stage 181 b as well as the liquid 187 b that provided to thesecond absorption stage since the ammonia-containing flue gas stream isentering the wash vessel 180 at the bottom is untreated and thereforehas the highest concentration of ammonia.

It should be appreciated that the amount of ammonia removed from theammonia-containing flue gas stream 170 varies from system to system andapplication to application. It is contemplated that the system isdesigned in a manner that the ammonia concentration in the reducedammonia containing flue gas stream 170 is low and close to anequilibrium concentration of ammonia in the gas relative to the vaporpressure of the ammonia in the liquid. The equilibrium concentration ofammonia in the flue gas stream 170 may be as low as below ten parts permillion (10 ppm) and typically in the range of between about zero partsper million (0 ppm) to about two hundred parts per million (200 ppm). Inone embodiment, the reduced ammonia containing flue gas stream 190contains at least about seventy percent (70%) less ammonia as comparedto a level of ammonia in the ammonia-containing flue gas stream 170. Inanother embodiment, the reduced ammonia containing flue gas stream 190contains at least about seventy five percent (75%) less ammonia ascompared to a level of ammonia in the ammonia-containing flue gas stream170. In yet a further embodiment, the reduced ammonia containing fluegas stream 190 contains at least about eighty percent (80%) less ammoniaas compared to a level of ammonia in the ammonia-containing flue gasstream 170. In another embodiment, the reduced ammonia containing fluegas stream 190 contains at least about eighty five (85%) less ammonia ascompared to a level of ammonia in the ammonia-containing flue gas stream170. It is contemplated that the level of ammonia in the reduced ammoniacontaining flue gas stream 190 may be about ninety percent (90%), ninetyfive percent (95%), ninety nine percent (99%) or ninety nine and a halfpercent (99.5%) less than the level of ammonia in the ammonia-containingflue gas stream 170.

A flow rate of liquid 187 suitable to reduce the amount of ammonia inthe flue gas varies from system to system. In one embodiment, the flowrate is suitable to reduce an amount of ammonia in the flue gas to anamount close to the equilibrium concentration and typically to below twohundred parts per million (200 ppm) in the flue gas stream. In anotherembodiment, the flow rate is suitable to reduce an amount of ammonia inthe flue gas from about two thousand parts per million (2000 ppm) tobetween about seventy parts per million and about one hundred parts permillion (70-100 ppm). In another embodiment, the flow rate of the liquid187 is between about 1.8 liters per minute (1.8 lpm, or about 0.5gallons per minute) to about 7.5 liters per minute (7.5 lpm or about 2gallons per minute) per one thousand cubic feet per minute (1000 cfm) offlue gas.

Still referring to FIG. 3, the liquid 187 falls to the bottom of thewash vessel 180 and is removed therefrom as ammonia-rich liquid 192. Asshown in FIG. 3, in one embodiment, a portion of the ammonia-rich liquid192 is recycled to the wash vessel 180 as liquid 187 and a portion ofthe ammonia-rich liquid is sent to the stripping column 194 (shown inFIG. 1). For example, a portion of the ammonia-rich liquid 192 is cooledin a heat exchanger 189 and recycled to second absorption stage 181 b asliquid 187 b. While not illustrated, it is contemplated that a portionof the ammonia-rich liquid 192 may be recycled from the bottom of thewash vessel 180 to first absorption stage 181 a as liquid 187 a.Additionally, while not shown, it is contemplated that the entire amountof the ammonia-rich liquid 192 may be sent to the stripping column 194and then returned to the wash vessel 180 as liquid 187 a.

Still referring to FIG. 3, the portion of ammonia-rich liquid 192 sentto stripping column 194 is regenerated to form liquid 187 a which isintroduced via spray head system 186 in first absorption stage 181 a. Inthe stripping column 194, the ammonia, as well as other contaminants,such as CO₂, is removed from the ammonia-rich liquid 192 to form theliquid 187 a, which may be water, or water having, for example, tracecontaminants of ammonia. When introduced in this manner, the liquid 187a that is introduced to the first absorption stage 181 a is referred toas “once through liquid” since it is “clean liquid” that has not beenrecycled from the bottom of the wash vessel 180.

In one embodiment, stripping column 194 utilizes steam to removeammonia, as well as other contaminants, from the ammonia-rich liquid 192to form the liquid 187 that will be introduced to the wash vessel 180.However, it is contemplated that stripping column 194 may utilize othertechnology or techniques in order to remove the ammonia and othercontaminants from the ammonia-rich liquid 192. In one embodiment, thestripping column 194 may be operated at vacuum conditions to reduce thetemperature of the steam utilized in the stripping column.

While not shown in FIG. 1, it is contemplated that the ammonia removedfrom ammonia-rich liquid 192 may be re-utilized within system 100. Forexample, the ammonia may be introduced in the absorbing system 130 asammoniated solution or slurry 150. However, it is contemplated that theammonia may be utilized at other points inside and outside of system100.

The amount of ammonia released to the environment is reduced orsubstantially eliminated by passing an ammonia-containing flue gasstream through wash vessel 180. The amount of liquid 187 introduced tothe various absorption stages 181, e.g., liquid 187 a introduced to thefirst absorption stage 181 a and liquid 187 b introduced to the secondabsorption stage 181 b, may be controlled either continually or atpredetermined time periods, to some extent by an operator, depending on,for example, the amount or flow of flue gas introduced to the washvessel, a level of contaminants measured within emission from the system100, and the like. The ability to control an amount of water used in thesystem may facilitate the savings of resources and reduce operatingexpenses.

The following examples illustrate one or more embodiments describedherein. The examples are not meant to limit the subject matter disclosedherein, but rather to illustrate one or more of the embodiments.

EXAMPLES Example 1

Four trials (runs 95, 98, 99 and 100) are conducted in a system having awash vessel that includes 1-inch (2.54 cm) random Jaeger packing(available from Jaeger Products Inc., Houston, Tex., United States) inthe first absorption stage 181 a as shown in FIG. 3. A summary of theresults is provided in Tables 1-4.

Inlet ammonia concentration of the ammonia-containing flue gas streamentering the wash vessel varies between fifteen hundred and six thousandparts per million (1500-6000 ppm) at a constant gas flow rate. The testsare conducted with a flue gas stream containing ammonia as describedabove and a CO₂ concentration in the range of 0-2.3 v/v %. Liquidintroduced to the wash vessel is water having a temperature between 1-5°C., and the water flow rate is between 2 and 6.5 lpm.

TABLE 1 Trial No. 95 WATER WASH [NH3]g [NH3]g Liquid Gas Water delta RunCO2 inlet^(#) outlet^(#) Flow Flow Temp P WW Time v/v % ppmv ppmv lpmacfm (C.) inch-water min 0 6800 1200-1300 6.5 731 1.7 ~9 ~25 1.9 5500650 6.5 730 ~9 30 1.9 5000 450 6.5 730-740 1.5 to 2   ~9 39 0 3100 850~3 740 1.4 9.2 62 5.82 2000 80 ~3 211 1.3 4.1 80 ~1.9 2000 160 ~3 725 1to 2 ~9 85 2000 200 ~3 725 1 to 2 ~9 88 ~1.9 2000 110 6.5 707 1 to 2 ~998 ^(#)Dragger Tube

TABLE 2 Trial No. 98 WATER WASH [NH3]g [NH3]g Liquid Gas Water delta RunCO2 inlet^(#) outlet^(#) Flow Flow Temp P WW Time v/v % ppmv ppmv lpmacfm (C.) inch-water min 2.4 4000 1596* 5.5 730-740 4-5 9-10 27 2.4 40001229* 5.5 730-740 4-5 9-10 29 2.4 3500 976*, 600 5.5 730-740 4-5 9-10 352.4 3500 752*, 450 5.5 730-740 4-5 9-10 42 2.4 3000 644*, 350 5.5730-740 4-5 9-10 52 2.4 2900 353*, 325 5.5 730-740 4-5 9-10 62 2.4 2900260 5.5 730-740 4-5 9-10 75 ^(#)Dragger Tube *FTIR

TABLE 3 Trial No. 99 WATER WASH Change in Pressure [NH3]g [NH3]g LiquidGas Water (delta P) Run CO2 inlet^(#) outlet^(#) Flow Flow Temp WaterWash Time v/v % ppmv ppmv lpm acfm (C.) inch-water min 2.4 2200 766*,400 3.7 730-735 2-3 9-10 10 2.4 2200 400*, 400 4.0 730-735 2 9-10 18 2.42000 355*, 300 4.0 730-735 2 9-10 27 2.4 1950 400*, 350 1.8 730-735 19-10 45 2.4 1900 423*, 400 1.8 730-735 1 9-10 50 2.4 1850 440*, 400 1.8730-735 1 9-10 59 2.4 1800 450*, 400 1.8 730-735 1 9-10 69 2.4 1750235*, 210 3.7 730-735 2-3 9-10 81 2.4 1650 220*, 220 3.7 730-735 2-39-10 89 2.4 1600 100* 6.6 730-735 3 9-10 98 2.4 1500 76*, 80 6.6 730-7353 9-10 107 ^(#)Dragger Tube *FTIR

TABLE 4 Trial No. 100 WATER WASH [NH3]g [NH3]g Liquid Gas Water deltaRun CO2 inlet^(#) outlet^(#) Flow Flow Temp P WW Time v/v % ppmv ppmvlpm acfm (C.) inch-water min 2.4 1200 198*, 160 2 750 1-2 22 2.4 1200128 4 750 1-2 7.5 34 2.4 1200 55 6.5 750 1-2 8 47 ^(#)Dragger Tube *FTIRIn tables 1-4, the ammonia inlet and ammonia outlet refer to theconcentration of ammonia in the ammonia-containing flue gas streamentering the wash vessel and the reduced ammonia containing flue gasstream exiting the wash vessel. The change in pressure (delta P) is thepressure drop measured across the wash vessel. “ACFM” refers to actualcubic feet per minute, which is the volumetric flow rate of the flue gasstream at the actual pressure and temperature. The “water temp” refersto the water used in the wash vessel, the “liquid flow” refers to flowrate of the water in the wash vessel and the “gas flow” refers to theflow rate of the flue gas stream through the wash vessel.

Example 2

Three trials (101, 102, and 103) are conducted to test the performanceof a system utilizing a wash vessel having 2-inch (about 5.1 cm) randomJaeger packing (available from Jaeger Products Inc., Houston, Tex.,United States) in the first absorption stage of a wash vessel, similarto first absorption stage 181 a in a wash vessel 180 shown in FIG. 3.The results are given in Tables 5-7.

During these runs, inlet ammonia concentration varies from betweenthirteen hundred and four thousand parts per million (1300-4000 ppm) ata 800-833 standard cubic feet per minute (scfm) corresponding to about 8feet per second gas. The concentration of CO₂ in the air is 0-2.3 v/v %.The scrubbing water temperature is 3-9° C., and the water flow rates are2, 4, and 6 lpm.

TABLE 5 Summary data from Run No. 101 WATER WASH [NH3]g [NH3]g LiquidGas Water delta Liquid at Air CO2 inlet^(#) outlet^(#) Flow Flow Temp PWW the bottom In/out v/v % ppmv ppmv lpm acfm(scfm) (C.) inch-water ° C.° C. 2.2 2800 700, 750* 2 692 (806) 3.5 >5 2.6 3.7/6.2 2.2 2800 225 4714 (811) 4.9 >5 2.7 3.6/6.9 2.2 2800 98 6 714 (811) 3.0 >5 3.5 4.1/5.9*FTIR readings ^(#)Dragger Tube readings

TABLE 6 Summary data from Run No. 102 WATER WASH [NH3]g [NH3]g LiquidGas Water delta Liquid at Air CO2 inlet^(#) outlet^(#) Flow Flow Temp PWW the bottom In/out v/v % ppmv ppmv lpm acfm(scfm) (C.) inch-water ° C.° C. 2.2 2000 630* 2 719 (~800) 7.7 >5 9.2  9.5/11.5 2.2 2000 285* 4 718(829) 7.8 >5 9.2 9.7/11  2.2 2000  98* 6 714 (823) 8.1 >5 9.2 9.8/11 2.2 1400 320* 2 711 (~820) 3.6 >5 5.8 6.3/8.4 2.2 1300  80* 4 711 (811)3.5 >5 2.2 1300  68* 6 711 (~820) 3.5 >5 5.5 5.8/7.4 0 1350 400* 4 704(802) 4.1 >5 5.1 5.5/7.0 *FTIR readings ^(#)Dragger tube readings

TABLE 7 Summary data from Run No. 103 WATER WASH [NH3]g [NH3]g LiquidGas Water delta Liquid at Air CO2 inlet^(#) outlet^(#) Flow Flow Temp PWW the bottom In/out v/v % ppmv ppmv lpm acfm(scfm) (C.) inch-water ° C.° C. 2.3 4000 1458*  2 742 (833) 5.1 >5 7.7  9.5/10.6 2.3 4000 670* 4743 (833) 5.3 >5 7.1 8.8/9.7 2.3 4000 355* 6   740 (~830) 4.9 >5 7.18.5/9.8 *FTIR readings ^(#)Dragger tube readingsIn tables 5-7, the ammonia inlet and ammonia outlet refer to theconcentration of ammonia in the ammonia-containing flue gas streamentering the wash vessel and the reduced ammonia containing flue gasstream exiting the wash vessel. The change in pressure (delta P) is thepressure drop measured across the wash vessel. “ACFM” refers to actualcubic feet per minute, which is the volumetric flow rate of the flue gasstream at the actual pressure and temperature. The “water temp” refersto the water used in the wash vessel, the “liquid flow” refers to flowrate of the water in the wash vessel and the “gas flow” refers to theflow rate of the flue gas stream through the wash vessel.

Example 3

Three trials (104, 105, and 106) are conducted to measure theeffectiveness of wood packing as the mass transfer device in the washvessel to remove ammonia from an ammonia-containing flue gas streamcontaining 600 to 3500 ppm ammonia and 0-2.3 v/v % CO₂. The temperatureof the water is 2-7° C. During most of these tests, the gas flow rate iskept in the range 730 to 750 scfm, and the outlet ammonia concentrationis measured under varying water flow rates (2, 4, 6 lpm). Summary of theresults are given in Table 8.

TABLE 8 Summary data from Trials 104, 105 and 106 WATER WASH [NH3]g[NH3]g Liquid Gas Water delta Liquid at Air CO2 inlet^(#) outlet^(#)Flow Flow Temp P WW the bottom In/out v/v % ppmv ppmv lpm acfm(scfm)(C.) inch-water ° C. ° C. Run No. 104 0  600  425* 2 700 (~730) 4.9 1.74.4 4.0/7.4 0  600  280* 4 700 (~730) 3.3 2.2 4.0 4.0/6.1 0  600  180* 6699 (~730) 3.3 2.3 4.3 4.1/5.9 0 1500 1000* 2 699 (~730) 3.9 1.8 4.44.3/6.4 0 1500  650* 4 699 (~730) 3.4 — 4.1 3.9/5.8 0 1500  400* 6 699(~730) 2.8 2.4 4.2 5.0/6.0 0 3500 1900* 2 699 (~730) 2.5-3.5 2.1 — — 03500 1450  4 699 (~730) 2.5-3.5 2.3 — — 0 3500 988 6 699 (~730) 2.5-3.52.4 — — 2.3 3000 1250  2 720 (~754) 4.3 1.9 5.9 6.5/8.1 2.3 3000 520 4720 (~754) 4.0-4.5 — — — 2.3 3000 480 6 720 (~754) 4.0-4.5 — — — 0 30001255  6 720 (~754) 4.0-4.5 — — — 2.3 3000 1067  2 720 (~754) 4.0-4.5 2.3— — 2.3 3000 609 4 720 (~754) 4.0-4.5 2.4 — — 2.3 3000 440 6 720 (~754)4.0-4.5 2.6 — — 2.3 1400 500 2 720 (~754) 4.0-4.5 2.3 — — 2.3 1400 317 4720 (~754) 4.0-4.5 — — — 2.3 1400 160 6 720 (~754) 4.0-4.5 — — — Run No.105 2.2 2000  850* 2 716 (745)   6.5 2.0 8     7/11.9 2.2 2000  850* 2716 (745)   — — — — 2.2 2000  723* 2 716 (745)   4.3 — 5.2 5.6/7.7 2.22100  840* 2 716 (745)   — — — — 2.2 2000  723* 2 716 (745)   — — — —2.2 2000 715 2 716 (745)   — — — — 2.2 2000 475 4 716 (745)   — — — —2.2 2000 280 6 716 (745)   — — — — 2.2 2000 619 2 715 (745)   — — — —2.2 2000 564 2 606 (617)   — — — — 2.2 2000 347 2 423 (427)   — — — —2.2 1700 655 2 702 (732)   — — — — Run No. 106 2.2  500*  200* 2 716(745)   3.5 2.3 5.6 5.9/9.1 2.2  500*  55* 6 716 (745)   3.7 2.7 5.66.2/7.1 *FTIR readings ^(#)Dragger tube readingsIn table 8, the ammonia inlet and ammonia outlet refer to theconcentration of ammonia in the ammonia-containing flue gas streamentering the wash vessel and the reduced ammonia containing flue gasstream exiting the wash vessel. The change in pressure (delta P) is thepressure drop measured across the wash vessel. “ACFM” refers to actualcubic feet per minute, which is the volumetric flow rate of the flue gasstream at the actual pressure and temperature. The “water temp” refersto the water used in the wash vessel, the “liquid flow” refers to flowrate of the water in the wash vessel and the “gas flow” refers to theflow rate of the flue gas stream through the wash vessel.

The terms “first,” “second,” and the like, herein do not denote anyorder, quantity, or importance, but rather are used to distinguish oneelement from another. The terms “a” and “an” herein do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced item.

While the invention has been described with reference to variousexemplary embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A method of reducing an amount of ammonia in a CO2 lean flue gasstream resulting from an ammonia-based CO2 capture system, the methodcomprising: contacting a flue gas stream with an ammoniated slurry orsolution within an absorption tower, wherein the ammoniated slurry orsolution removes carbon dioxide (CO₂) from the cooled flue gas streamthereby forming an ammonia-containing flue gas stream; and introducingat least a portion of the ammonia-containing flue gas stream from theabsorption tower to a wash vessel, the wash vessel having first andsecond absorption stages to absorb ammonia from the ammonia-containingflue gas stream thereby reducing an amount of ammonia in a flue gasstream exiting the wash vessel, each of the first and second absorptionstages including a mass transfer device and a liquid delivery path;introducing a first liquid to the liquid delivery path of the firstabsorption stage such that the first liquid flows in a directioncountercurrent to the ammonia-containing flue gas stream to contact theammonia-containing flue gas stream and the mass transfer devices of thefirst and second absorption stages; introducing a second liquid having adifferent ammonia content than the first liquid to the liquid deliverypath of the second absorption stage such that the second liquid flows ina direction countercurrent to the ammonia-containing flue gas stream tocontact the ammonia-containing flue gas stream and the mass transferdevice of the second absorption stage, whereby the first and secondliquids absorb ammonia from the ammonia-containing flue gas stream.
 2. Amethod according to claim 1, wherein the second liquid has a higherammonia content than the first liquid.
 3. A method according to claim 2,further comprising: collecting the first and second liquids in the washvessel; removing the collected first and second liquids from the washvessel; and providing at least a portion of the removed first and secondliquids to the liquid delivery path of the second absorption stage asthe second liquid.
 4. A method according to claim 3, further comprisingproviding a portion of the removed first and second liquids to astripping column; removing ammonia from the portion of the removed firstand second liquids in the stripping column to produce the first liquidfor introduction to the liquid delivery path of the first absorptionstage.
 5. A method according to claim 2 wherein the first liquid iswater and the second liquid is water containing ammonia.
 6. A methodaccording to claim 1, wherein the liquid delivery path of each of thefirst and second absorption stages includes a spray head systempositioned above the mass transfer device for introducing the liquid tothe absorption stage.
 7. A method according to claim 1, wherein the masstransfer device of at least one of the first and second absorptionstages comprises a hydrophilic packing material.
 8. A method accordingto claim 1, wherein the mass transfer device of at least one of thefirst and second absorption stages comprises structural packing.
 9. Amethod according to claim 1, wherein the mass transfer device of atleast one of the first and second absorption stages comprises randompacking material.
 10. A method according to claim 1, wherein the masstransfer device of the first absorption stage comprises a differentpacking material than the mass transfer device of the second absorptionstage.
 11. A method according to claim 10, wherein the mass transferdevice of one of the first absorption stage and the second absorptionstage comprises random packing material and the mass transfer device ofthe other of the first absorption stage and the second absorption stagecomprises structural packing material.
 12. A method according to claim11, wherein the mass transfer device of the first absorption stagecomprises random packing material and the mass transfer device of thesecond absorption stage comprises structural packing material.